RF MEMS realize “ideal switching”.

Twenty years ago, professional engineers in RF circuits envisioned an “ideal switch.” This switch has very low resistance “on” and very high resistance “off”, it is small, fast, easy to manufacture, capable of switching considerable currents, and can withstand billions of switches Converting, switching requires very little power. It also conducts signals from tens to hundreds of gigahertz without distortion (near-perfect linearity).

This is not a fantasy, this large emerging industry market is ready. As microelectromechanical systems (MEMS) continue to make breakthroughs, large-scale projects have sprung up in the United States and Europe. Many projects are funded by the U.S. Defense Advanced Research Projects Agency (DARPA) or the European Union Network of Excellence. Entering the 21st century, after a long and turbulent technological development, radio frequency microelectromechanical systems (RF MEMS) switches are now finally on their way to commercial success.

In the US, there are two companies that are likely to grow quickly and gain a foothold in a competitive market. One is Menlo Micro, a subsidiary of GE Ventures, located in Irvine, California. The company’s co-founder and senior vice president Chris? Chris Giovaniello said they have more than 30 customers in the aerospace, military and wireless network infrastructure industries. Meanwhile, there is a Silicon Valley company called Cavendish Kinetics, which is developing RF MEMS switches for smartphones. In October 2019, the company was acquired by Qorvo Corporation, a leading manufacturer of wireless devices and systems, many of which are used in smartphones. While specific terms of the acquisition were not disclosed, Cavendish has raised more than $58 million in at least three rounds of funding.

This success has come after a long and turbulent time, with high hopes and low hopes. “Many companies tried, and only these two succeeded, and they were lucky. Maybe 20 failed, and that’s the reality. For tech startups, a 10 percent success rate is pretty normal.” RF MEMS research and development pioneer, UC San Diego electrical engineering professor Gabriel? Gabriel Rebeiz said.

The new device combines the best features of electromechanical relay switches (ultra-low resistance and leakage current and very high linearity) with some of the advantages of semiconductor switches (small size, very high reliability, robustness). Conceptually, this device is similar to a relay switch. In operation, electrostatic forces pull a conductive beam (also called an actuator or cantilever) toward the electrical contacts. Unlike relays, whose action is triggered by an electromagnet, RF MEMS switches use a DC voltage of 50 to 100 volts to create an electrostatic field that pulls a conductive beam to the electrical contacts. Since the electric field is static, the current and power consumption are very low.

The hardest technical challenge, Giovanniello said, was finding a conductive alloy that could withstand billions of repeated bends. He said: “The real problem is the actuator, and to solve that problem GM has put a lot of effort into developing alloys. We have developed some highly conductive proprietary alloys that are great for relays, but are extremely mechanically strong. High, very much like polysilicon.”

“General has done a lot of work on alloys for jet engines for decades, and in fact, it’s some of them that help us solve some fundamental reliability problems,” he added. Menlo has not disclosed its alloys. However, research papers written by engineers at GM and Menlo about 5 years ago indicate that they were working on nickel and gold alloys, respectively.

Meanwhile, Qorvo is targeting apps inside smartphones (as is Menlo Micro). Qorvo’s director of technology development Julio? About 1.5 billion smartphones are sold each year, which is a huge market with extremely strict requirements for devices, Julio Costa said. “Mobile phones are an important part of people’s daily lives, so if (new devices) are not reliable, they cannot be used.”

There are several main uses for devices in smartphones, Costa explained. The first use that Qorvo is pursuing is antenna tuning. To accommodate the increasing frequency bands of wireless networks transitioning from 4G to 5G, modern smartphones have up to eight antennas. In order to better match the antenna and frequency, the switch embedded in the antenna can change the configuration, and connect resonant elements such as capacitors or inductors to achieve fine-tuning of the antenna response. Mobile phone manufacturers currently use semiconductor switches based on silicon-on-insulator (SOI) technology for this application. But the higher frequency and linearity of MEMS devices could make them an attractive alternative, especially for certain 5G bands, Costa said. He hopes to integrate these switches into phones “within a few years.”

Giovanniello said in a remote interview that the use of wireless networking, radar and instrumentation is just the beginning. He claims that Menlo Micro has used a microswitch to conduct 20 amps of current, and he envisions the device serving as a “resettable, electronically controlled fuse” in the future.

He added: “Every few generations, a new technology emerges that offers a different way of making switches. How we love to portray this ideal switching technology. It’s a combination of the best of mechanics and semiconductors. , but at the end of the day, it’s a new process technology for making switches that we and our partners will be producing in the next 10 years with hundreds of different products.”


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